Possible Future Sources of Natural Gas

One experimental idea is to use the methane gas that is naturally produced from landfills to supply power to cities. Tests have shown that methane gas could be a financially sustainable power source.

There are plans in Ontario to capture the biogas, methane gases rising from the manure of cattle caged in a factory farm, and to use that gas to provide power to a small town. There is also the possibility that with the source separation of organic materials from the waste stream that by using an anaerobic digester, the methane can be used to produce usable energy. This can be improved by adding other organic material (plants as well as slaughter house waste) to the digester. A speculative source of enormous quantities of methane is from methane hydrate, found under sediments in the oceans. At present (2006), no technology has been developed to recover this source of energy economically.

In any form, a minute amount of odorant such as methyl mercaptan, with a rotting-cabbage-like smell, is added to the otherwise colourless and odorless gas, so that leaks can be detected before a fire or explosion occurs. Sometimes a related compound, ethyl mercaptan is used, with a rotten-egg smell. Adding odorant to natural gas began in the United States after the 1937 New London School explosion. The buildup of gas in the school went unnoticed, killing three hundred students and faculty when it ignited.

Although concentrated thiols are extremely toxic, it is considered non-toxic in the extremely low concentrations in which it occurs in natural gas delivered to the end user. For example, a safe exposure level to ethyl mercaptan at 5 parts per million over an eight-hour period has been established by the American Congress of Government and Industrial Hygienists (ACGIH).

Actual concentrations used by gas companies are on the order of 5 parts per billion (5 parts in 109), one-thousandth the maximum safe limit. In mines, where methane seeping from rock formations has no odor, sensors are used, and mining apparatus has been specifically developed to avoid ignition sources, e.g., the Davy lamp.

Explosions caused by natural gas leaks occur a few times each year. Individual homes, small businesses and boats are most frequently affected when an internal leak builds up gas inside the structure. Frequently, the blast will be enough to significantly damage a building but leave it standing. In these cases, the people inside tend to have minor to moderate injuries. Occasionally, the gas can collect in high enough quantities to cause a deadly explosion, disintegrating one or more buildings in the process. The gas usually dissipates readily outdoors, but can sometimes collect in dangerous quantities if weather conditions are right. Also, considering the tens of millions of structures that use the fuel, the individual risk of using natural gas is very low.

Some gas fields yield sour gas containing hydrogen sulfide. This untreated gas is toxic. Extraction of natural gas (or oil) leads to decrease in pressure in the reservoir. This in turn may lead to subsidence at ground level. Subsidence may affect ecosystems, waterways, sewer and water supply systems, foundations, etc.

Дата добавления: 2015-10-21